Light emitting device reflective bank structure

ABSTRACT

Reflective bank structures for light emitting devices are described. The reflective bank structure may include a substrate, an insulating layer on the substrate, and an array of bank openings in the insulating layer with each bank opening including a bottom surface and sidewalls. A reflective layer spans sidewalls of each of the bank openings in the insulating layer.

RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 16/998,917, filed Aug. 20, 2020, which is a continuation ofU.S. patent application Ser. No. 16/028,611, filed Jul. 6, 2018, nowU.S. Pat. No. 10,784,236, which is a continuation of U.S. patentapplication Ser. No. 15/426,947, filed Feb. 7, 2017, now U.S. Pat. No.10,043,784, which is a continuation of U.S. patent application Ser. No.14/864,570, filed Sep. 24, 2015, now U.S. Pat. No. 9,620,487, which is acontinuation of U.S. patent application Ser. No. 13/710,443, filed onDec. 10, 2012, now U.S. Pat. No. 9,178,123 which is incorporated hereinby reference.

BACKGROUND Field

The present invention relates to a reflective bank structure for lightemitting devices. More particularly, embodiments of the presentinvention relate to a reflective bank structure for light emitting diodedevices.

Background Information

Light emitting diode (LED) devices may include a p-type semiconductorlayer, an n-type semiconductor layer, and one or more quantum welllayers between the p-type semiconductor layer and the n-typesemiconductor layer. The light emitting efficiency of a LED devicesystem depends upon the internal quantum efficiency of the quantum welllayer(s) and the light extraction efficiency from the system.

One implementation for increasing light extraction efficiency has beento include a reflective layer in the electrode layer opposite the lightemission direction. For example, for a top emission structure, thebottom electrode may include a reflective layer, and vice versa. Lightemitting from the lateral surfaces of a LED device may decrease lightextraction efficiency.

One implementation for increasing light extraction efficiency from ahorizontal LED chip is described in U.S. Pat. No. 7,482,696 in which ahorizontal LED chip is placed within a cavity of an insulating submountwith a pair of conductive-reflective films on sidewalls of the cavity.An n-side electrode on a bottom side surface of the horizontal LED chipis flip chip bonded to a pad on one of the conductive-reflective films,and a p-side electrode on the bottom side surface of the horizontal LEDchip is flip chip bonded to a pad on the other conductive-reflectivefilm. In this manner, the horizontal LED chip is packaged within thesubmount, and lateral emission through the side surfaces of thehorizontal LED chip is reflected to increase light extraction efficiencyof the package.

One implementation for increasing light extraction efficiency from avertical LED device system is described in U.S. Pat. No. 7,884,543 inwhich a light emitting surface of the vertical LED device is mounted ona narrow wiring in a transparent substrate. A transparent resin isformed over and around the vertical LED device, and a reflective film isdeposited over the transparent resin and the vertical LED device todirect light toward the light emitting surface.

SUMMARY OF THE INVENTION

Reflective bank structures for light emitting devices are described. Inan embodiment, a reflective bank structure includes a substrate, aninsulating layer on the substrate, an array of bank openings in theinsulating layer, with each bank opening including a bottom surface andsidewalls, and a reflective layer spanning the sidewalls of each of thebank openings in the insulating layer. Each of the bank openings mayhave a width or height to accept a light emitting device. In anembodiment, each light emitting device is a vertical LED device. Wherethe light emitting devices are micro devices, such as vertical micro LEDdevices having a maximum width or length of 1 to 100 μm, each bankopening may have a maximum width or length of 1 to 100 μm or slightlylarger to accommodate mounting of the array of vertical micro LEDdevices within the corresponding array of bank openings. In anembodiment, each vertical LED device has a top surface that is above atop surface of the insulating layer. Each vertical LED device mayinclude a top conductive electrode and a bottom conductive electrode.

In an embodiment, a transparent passivation layer is formed that spanssidewalls of the array of vertical LED devices and at least partiallyfills the array of bank openings. For example, the transparentpassivation layer may span and cover a quantum well structure within thearray of vertical LED devices. In an embodiment, the transparentpassivation layer does not completely cover the top conductive electrodeof each vertical LED device. In this manner, a transparent conductorlayer can be formed over and in electrical contact with the topconductive electrode, if present, for each vertical LED device.

The reflective layer may have a variety of configurations in accordancewith embodiments of the invention. For example, the reflective layer maycompletely, or only partially, span the sidewalls of each of the bankopenings. For example, the reflective layer may completely, onlypartially, or not cover the bottom surface of each of the bank openings.In an embodiment, the reflective layer is a continuous layer formed overthe insulating layer and the substrate within the array of bank openingsin the insulating and completely spans the sidewalls and covers thebottom surface of each of the bank openings.

The reflective layer may also be patterned. In an embodiment, thereflective layer is a patterned layer including an array of reflectivebank layers corresponding to the array of bank openings, where eachreflective bank layer spans the sidewalls of a corresponding bankopening. For example, the reflective layer may completely, or onlypartially, span the sidewalls of each of the bank openings. For example,the reflective layer may completely, only partially, or not cover thebottom surface of each of the bank openings. In an embodiment, eachreflective bank layer does not cover a center of the bottom surface of acorresponding bank opening. In an embodiment, each reflective bank layerincludes a sidewall layer that spans the sidewalls of the correspondingbank openings and a separate pad layer on the bottom surface thecorresponding bank opening. In an embodiment, the sidewalls of each ofthe bank openings is characterized by a first and second laterallyopposite sidewalls, and each reflective bank layer spans the firstlaterally opposite sidewall and does not span the second laterallyopposite sidewall.

Embodiments of the invention may be utilized to incorporate a reflectivebank structure on a variety of substrates, such as lighting or displaysubstrates. In some embodiments, an integrated circuit may beincorporated within the substrate. For example a corresponding array ofintegrated circuits may be interconnected with the bottom surfaces ofthe array of bank openings. In some embodiments, an electrical line outor array of electrical lines out are interconnected with the bottomsurfaces of the array of bank openings.

In an embodiment, a via opening is formed in the insulating layer. Anelectrical line out may be formed at the bottom surface of the viaopening. In an embodiment, the via opening is connected with anintegrated circuit in an underlying substrate. In an embodiment, anarray of vertical LED devices are mounted within the corresponding arrayof bank openings and a transparent conductor layer is formed over and inelectrical contact with the electrical line out and each vertical LEDdevice. The patterned reflective layer may further include the array ofreflective bank layers within the array of bank openings and a separatereflective via layer within the via opening.

In an embodiment, the patterned reflective layer includes the array ofreflective bank layers within the array of bank openings and a separatereflective electrical line out on the insulating layer. In anembodiment, an array of vertical LED devices are mounted within thecorresponding array of bank openings and a transparent conductor layeris formed over and in electrical contact with the electrical line outand each vertical LED device.

In an embodiment, an array of via openings are formed in the insulatinglayer. An array of electrical lines out may be formed at the bottomsurface of each of the corresponding array of via openings. In anembodiment, the array of via openings are connected with an array ofintegrated circuits in an underlying substrate. In an embodiment, anarray of vertical LED devices are mounted within the corresponding arrayof bank openings and an array of transparent conductor layers areformed, with each transparent conductor layer formed over and inelectrical contact with a corresponding electrical line out and acorresponding vertical LED device. The patterned reflective layer mayfurther include the array of reflective bank layers within the array ofbank openings and an array of separate reflective via layers within thearray of via openings.

In an embodiment, the patterned reflective layer includes the array ofreflective bank layers within the array of bank openings and a separatearray of reflective electrical lines out on the insulating layer. In anembodiment, an array of vertical LED devices are mounted within thecorresponding array of bank openings and an array of transparentconductor layers are formed, with each transparent conductor layerformed over and in electrical contact with a corresponding electricalline out and a corresponding vertical LED device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional side view illustration of an insulatinglayer formed on a substrate in accordance with an embodiment of theinvention.

FIG. 2A is a cross-sectional side view illustration of an array of bankopenings formed in an insulating layer in accordance with an embodimentof the invention.

FIG. 2B is a cross-sectional side view illustration of an array of bankopenings formed in an insulating layer in accordance with an embodimentof the invention.

FIG. 2C is a cross-sectional side view illustration of an array of bankopenings and a corresponding array of via openings formed in aninsulating layer in accordance with an embodiment of the invention.

FIG. 2D is a cross-sectional side view illustration of an array of bankopenings and a via opening formed in an insulating layer in accordancewith an embodiment of the invention.

FIG. 2E is a cross-sectional side view illustration of an array of bankopenings formed in an insulating layer over a substrate includingcircuitry in accordance with an embodiment of the invention.

FIG. 2F is a cross-sectional side view illustration of an array of bankopenings and a corresponding array of via openings formed in aninsulating layer over a substrate including circuitry in accordance withan embodiment of the invention.

FIG. 2G is a cross-sectional side view illustration of an array of bankopenings and a via opening formed in an insulating layer over asubstrate including circuitry in accordance with an embodiment of theinvention.

FIG. 2H is a cross-sectional side view illustration of an array of bankopenings formed in an insulating layer over a substrate includingcircuitry in accordance with an embodiment of the invention.

FIG. 2I is a cross-sectional side view illustration of an array of bankopenings and a corresponding array of via openings formed in aninsulating layer over a substrate including circuitry in accordance withan embodiment of the invention.

FIG. 2J is a cross-sectional side view illustration of an array of bankopenings and a via opening formed in an insulating layer over asubstrate including circuitry in accordance with an embodiment of theinvention.

FIG. 3A is a cross-sectional side view illustration of a continuousreflective layer formed over an array of bank openings in accordancewith an embodiment of the invention.

FIG. 3B is a cross-sectional side view illustration of an array ofreflective bank layers formed over an array of bank openings inaccordance with an embodiment of the invention.

FIG. 3C is a cross-sectional side view illustration of an array ofbonding layers formed on an array of reflective bank layers inaccordance with an embodiment of the invention.

FIG. 3D is a cross-sectional side view illustration of an array of banklayers including a sidewall layer and a separate pad layer in accordancewith an embodiment of the invention.

FIG. 3E is a cross-sectional side view illustration of an array ofbonding layers formed on a bottom surface of an array of bank openingsin accordance with an embodiment of the invention.

FIG. 3F is a cross-sectional side view illustration of an array ofreflective bank layers and a corresponding array of reflective vialayers in accordance with an embodiment of the invention.

FIG. 3G is a cross-sectional side view illustration of an array ofreflective bank layers and a reflective via layer in accordance with anembodiment of the invention.

FIG. 3H is a cross-sectional side view illustration of an array ofreflective bank layers spanning one laterally opposite sidewall of anarray of bank openings, and a corresponding array of reflective vialayers in accordance with an embodiment of the invention.

FIG. 3I is a cross-sectional side view illustration of a reflective banklayer spanning one laterally opposite sidewall of a bank opening and areflective via layer in accordance with an embodiment of the invention.

FIG. 3J is a cross-sectional side view illustration of an array ofreflective bank layers spanning one laterally opposite sidewall of anarray of bank openings, and a corresponding array of reflective vialayers spanning the other laterally opposite sidewall of the array ofbank openings in accordance with an embodiment of the invention.

FIG. 3K is a cross-sectional side view illustration of a reflective banklayer spanning one laterally opposite sidewall of a bank opening and areflective via layer spanning the other laterally opposite sidewall ofthe bank opening in accordance with an embodiment of the invention.

FIG. 3L is a cross-sectional side view illustration of an array ofreflective bank layers spanning laterally opposite sidewalls of an arrayof bank openings, a corresponding array of reflective via layers, and acorresponding array of bonding layers on a bottom surface of the arrayof bank openings in accordance with an embodiment of the invention.

FIG. 3M is a cross-sectional side view illustration of an array ofreflective bank layers spanning laterally opposite sidewalls of an arrayof bank openings, a reflective via layer, and an array of bonding layerson a bottom surface of the array of bank opening in accordance with anembodiment of the invention.

FIG. 3N is a cross-sectional side view illustration of an array ofreflective bank layers spanning one laterally opposite sidewall of anarray of bank openings, a corresponding array of reflective via layersspanning the other laterally opposite sidewall of the array of bankopenings, and a corresponding array of bonding layers on a bottomsurface of the array of bank openings in accordance with an embodimentof the invention.

FIG. 3O is a cross-sectional side view illustration of a reflective banklayer spanning one laterally opposite sidewall of a bank opening, areflective via layer spanning the other laterally opposite sidewall ofthe bank opening, and a bonding layer on a bottom surface of the bankopening in accordance with an embodiment of the invention.

FIG. 3P is a cross-sectional side view illustration of an array ofreflective bank layers formed over a substrate including circuitry inaccordance with an embodiment of the invention.

FIG. 3Q is a cross-sectional side view illustration of an array ofreflective bank layers and a corresponding array of reflective vialayers formed over a substrate including circuitry in accordance with anembodiment of the invention.

FIG. 3R is a cross-sectional side view illustration of an array ofreflective bank layers and a reflective via layer formed over asubstrate including circuitry in accordance with an embodiment of theinvention.

FIG. 3S is a cross-sectional side view illustration of an array ofreflective bank layers and a corresponding array of reflective lines outformed over a substrate including circuitry in accordance with anembodiment of the invention.

FIG. 3T is a cross-sectional side view illustration of an array ofreflective bank layers formed over a substrate including circuitry inaccordance with an embodiment of the invention.

FIG. 3U is a cross-sectional side view illustration of an array ofreflective bank layers and a corresponding array of reflective vialayers formed over a substrate including circuitry in accordance with anembodiment of the invention.

FIG. 3V is a cross-sectional side view illustration of an array ofreflective bank layers and a reflective via layer formed over asubstrate including circuitry in accordance with an embodiment of theinvention.

FIG. 3W is a cross-sectional side view illustration of an array ofreflective bank layers and a corresponding array of reflective lines outformed over a substrate including circuitry in accordance with anembodiment of the invention.

FIGS. 4A-4F are cross-sectional side view illustrations of a method oftransferring an array of light emitting devices onto an array ofreflective bank structures in accordance with an embodiment of theinvention.

FIG. 5A is a cross-sectional side view illustration of an array ofvertical micro LEDs mounted within a reflective bank structure for a topemitting system in accordance with an embodiment of the invention.

FIG. 5B is a top view illustration of FIG. 5A in accordance with anembodiment of the invention.

FIG. 6A is a cross-sectional side view illustration of an array ofvertical micro LEDs mounted within a reflective bank structure for a topand bottom emitting system in accordance with an embodiment of theinvention.

FIG. 6B is a top view illustration of FIG. 6A in accordance with anembodiment of the invention.

FIGS. 7A-7B are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3A in accordance with embodiments of theinvention.

FIG. 7C is a top view illustration of FIG. 7A prior to formation of thesidewall passivation layer and top conductive contact in accordance withan embodiment of the invention.

FIGS. 7D-7E are cross-sectional side view illustrations of the array oflight emitting devices of FIG. 7A in electrical contact with anelectrical line out of FIG. 2A in accordance with embodiments of theinvention.

FIGS. 7F-7G are cross-sectional side view illustrations of the array oflight emitting devices of FIG. 7B in electrical contact with anelectrical line out of FIG. 2A in accordance with embodiments of theinvention.

FIGS. 8A-8B are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3B in accordance with embodiments of theinvention.

FIG. 8C is a top view illustration of FIG. 8A prior to formation of thesidewall passivation layer and top conductive contact in accordance withan embodiment of the invention.

FIGS. 8D-8E are cross-sectional side view illustrations of the array oflight emitting devices of FIG. 8A in electrical contact with anelectrical line out of FIG. 2A in accordance with embodiments of theinvention.

FIGS. 8F-8G are cross-sectional side view illustrations of the array oflight emitting devices of FIG. 8B in electrical contact with anelectrical line out of FIG. 2A in accordance with embodiments of theinvention.

FIGS. 9A-9B are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3D in accordance with embodiments of theinvention.

FIG. 9C is a top view illustration of FIG. 9A prior to formation of thesidewall passivation layer and top conductive contact in accordance withan embodiment of the invention.

FIG. 9D is a cross-sectional side view illustration of the array oflight emitting devices of FIG. 9A in electrical contact with anelectrical line out of FIG. 2B in accordance with an embodiment of theinvention.

FIG. 9E is a cross-sectional side view illustration of the array oflight emitting devices of FIG. 9B in electrical contact with anelectrical line out of FIG. 2B in accordance with an embodiment of theinvention.

FIGS. 10A-10B are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3F in accordance with embodiments of theinvention.

FIG. 10C is a top view illustration of FIG. 10A prior to formation ofthe sidewall passivation layer and top conductive contact in accordancewith an embodiment of the invention.

FIG. 10D is a top view illustration of FIG. 10A after formation of thesidewall passivation layer and top conductive contact in accordance withan embodiment of the invention.

FIGS. 10E-10F are cross-sectional side view illustrations of the arrayof light emitting devices of FIG. 10A in electrical contact with anelectrical line out of FIG. 2C in accordance with embodiments of theinvention.

FIGS. 10G-10H are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3F in electrical contact with anelectrical line out of FIG. 2C in accordance with embodiments of theinvention.

FIGS. 10I-10J are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3G in electrical contact with anelectrical line out of FIG. 2D in accordance with embodiments of theinvention.

FIGS. 11A-11B are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3H in accordance with embodiments of theinvention.

FIG. 11C is a top view illustration of FIG. 11A prior to formation ofthe sidewall passivation layer and top conductive contact in accordancewith an embodiment of the invention.

FIG. 11D is a top view illustration of FIG. 11A after formation of thesidewall passivation layer and top conductive contact in accordance withan embodiment of the invention.

FIGS. 11E-11F are cross-sectional side view illustrations of the arrayof light emitting devices of FIG. 11A in electrical contact with anelectrical line out of FIG. 2C in accordance with embodiments of theinvention.

FIGS. 11G-11H are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3H in electrical contact with anelectrical line out of FIG. 2C in accordance with embodiments of theinvention.

FIGS. 11I-11J are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3I in electrical contact with anelectrical line out of FIG. 2D in accordance with embodiments of theinvention.

FIGS. 12A-12B are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3J in accordance with embodiments of theinvention.

FIG. 12C is a top view illustration of FIG. 12A prior to formation ofthe sidewall passivation layer and top conductive contact in accordancewith an embodiment of the invention.

FIG. 12D is a top view illustration of FIG. 12A after formation of thesidewall passivation layer and top conductive contact in accordance withan embodiment of the invention.

FIGS. 12E-12F are cross-sectional side view illustrations of the arrayof light emitting devices of FIG. 12A in electrical contact with anelectrical line out of FIG. 2C in accordance with embodiments of theinvention.

FIGS. 12G-12H are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3J in electrical contact with anelectrical line out of FIG. 2C in accordance with embodiments of theinvention.

FIGS. 12I-12J are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3K in electrical contact with anelectrical line out of FIG. 2D in accordance with embodiments of theinvention.

FIGS. 13A-13B are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3E in accordance with embodiments of theinvention.

FIG. 13C is a top view illustration of FIG. 13A prior to formation ofthe sidewall passivation layer and top conductive contact in accordancewith an embodiment of the invention.

FIG. 13D is a cross-sectional side view illustration of the array oflight emitting devices of FIG. 13A in electrical contact with anelectrical line out of FIG. 2B in accordance with an embodiment of theinvention.

FIG. 13E is a cross-sectional side view illustration of the array oflight emitting devices of FIG. 13B in electrical contact with anelectrical line out of FIG. 2B in accordance with an embodiment of theinvention.

FIGS. 13F-13G are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3L in electrical contact with anelectrical line out of FIG. 2C in accordance with embodiments of theinvention.

FIGS. 13H-13I are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3M in electrical contact with anelectrical line out of FIG. 2D in accordance with embodiments of theinvention.

FIG. 13J-13K are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3N in electrical contact with anelectrical line out of FIG. 2C in accordance with embodiments of theinvention.

FIG. 13L-13M are cross-sectional side view illustration of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3O in electrical contact with anelectrical line out of FIG. 2D in accordance with embodiments of theinvention.

FIG. 14A-14B are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3P in accordance with embodiments of theinvention.

FIG. 14C is cross-sectional side view illustration of an array of lightemitting devices mounted within the reflective bank structure describedwith regard to FIG. 3Q in accordance with an embodiment of theinvention.

FIG. 14D is cross-sectional side view illustration of an array of lightemitting devices mounted within the reflective bank structure describedwith regard to FIG. 3R in accordance with an embodiment of theinvention.

FIGS. 14E-14G are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuresdescribed with regard to FIG. 3S in accordance with embodiments of theinvention.

FIG. 15A-15B are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3T in accordance with embodiments of theinvention.

FIG. 15C is cross-sectional side view illustration of an array of lightemitting devices mounted within the reflective bank structure describedwith regard to FIG. 3U in accordance with an embodiment of theinvention.

FIG. 15D is cross-sectional side view illustration of an array of lightemitting devices mounted within the reflective bank structure describedwith regard to FIG. 3V in accordance with an embodiment of theinvention.

FIGS. 15E-15G are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuresdescribed with regard to FIG. 3W in accordance with embodiments of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention describe a reflective bankstructure for receiving light emitting devices such as LED devices. Forexample, the reflective bank structure may be formed on a receivingsubstrate such as, but not limited to, a display substrate, a lightingsubstrate, a substrate with functional devices such as transistors orintegrated circuits (ICs), or a substrate with metal redistributionlines. While some embodiments of the present invention are describedwith specific regard to vertical micro LED devices comprising p-ndiodes, it is to be appreciated that embodiments of the invention arenot so limited and that certain embodiments may also be applicable toother devices which are designed to perform a photonic function (LED,superluminescent diode (SLD), laser).

The terms “micro” device or “micro” LED structure as used herein mayrefer to the descriptive size of certain devices or structures inaccordance with embodiments of the invention. As used herein, the terms“micro” devices or structures are meant to refer to the scale of 1 to100 μm. However, it is to be appreciated that embodiments of the presentinvention are not necessarily so limited, and that certain aspects ofthe embodiments may be applicable to larger, and possibly smaller sizescales. In an embodiment, a single micro LED device has a maximumdimension, for example length and/or width, of 1 to 100 μm.

In various embodiments, description is made with reference to figures.However, certain embodiments may be practiced without one or more ofthese specific details, or in combination with other known methods andconfigurations. In the following description, numerous specific detailsare set forth, such as specific configurations, dimensions andprocesses, etc., in order to provide a thorough understanding of thepresent invention. In other instances, well-known semiconductorprocesses and manufacturing techniques have not been described inparticular detail in order to not unnecessarily obscure the presentinvention. Reference throughout this specification to “one embodiment”means that a particular feature, structure, configuration, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the invention. Thus, the appearances ofthe phrase “in one embodiment” in various places throughout thisspecification are not necessarily referring to the same embodiment ofthe invention. Furthermore, the particular features, structures,configurations, or characteristics may be combined in any suitablemanner in one or more embodiments.

The terms “spanning,” “over,” “to,” “between,” and “on” as used hereinmay refer to a relative position of one layer with respect to otherlayers. One layer “spanning,” “over,” or “on” another layer or bonded“to” another layer may be directly in contact with the other layer ormay have one or more intervening layers. One layer “between” layers maybe directly in contact with the layers or may have one or moreintervening layers.

In one aspect, embodiments of the invention describe a reflective bankstructure to increase light extraction efficiency from an array of lightemitting devices. In an embodiment, a reflective bank structure includesa substrate, an insulating layer, an array of bank openings in theinsulating layer with each bank opening including a bottom surface andsidewalls, and a reflective layer spanning the sidewalls of each of thebank openings in the insulating layer. Light emitting laterally from thelight emitting devices can be reflected from the sidewalls in a lightemitting direction of the system. Accordingly, in accordance withembodiments of the invention, lateral side emission may be a significantcontribution to light emission efficiency.

In another aspect, embodiments of the invention describe a reflectivebank structure to increase light extraction efficiency from an array ofvertical LED devices. The vertical LED devices mounted within the arrayof bank openings can include top and bottom electrodes. For example, thetop and bottom electrodes may have been annealed to provide ohmiccontacts with the p-n diode layer of the vertical LED device. Inaddition, the top and bottom electrodes may be transparent,semi-transparent, opaque, or include a reflective layer. In this manner,the reflective bank structure can incorporate a variety of shapes ofvertical LED devices, and is not limited to light emission from thevertical LED devices in the light emitting direction of the system.

In another aspect, embodiments of the invention describe a reflectivebank structure for receiving an array of light emitting devices on areceiving substrate. In an embodiment, an array of light emittingdevices are transferred from a carrier substrate to the receivingsubstrate with an array of transfer heads, which may be operated inaccordance with electrostatic principles. Without being limited to aparticular theory, embodiments of the invention utilize transfer headsand head arrays which operate in accordance with principles ofelectrostatic grippers, using the attraction of opposite charges to pickup micro devices. In accordance with embodiments of the presentinvention, a pull-in voltage is applied to a transfer head in order togenerate a grip pressure on a light emitting device and pick up thelight emitting device. In an embodiment, a grip pressure of greater than1 atmosphere is generated. For example, each transfer head may generatea grip pressure of 2 atmospheres or greater, or even 20 atmospheres orgreater without shorting due to dielectric breakdown of the transferheads. In some embodiments, the transfer heads in the micro pick uparray are separated by a pitch (x, y, and/or diagonal) that matches apitch on the receiving substrate for the array of light emittingdevices. For example, where the receiving substrate is a displaysubstrate the pitch of the transfer heads may match the pitch of thepixel or subpixel array. Table 1 provides a list of exemplaryimplementation in accordance with embodiments of the invention forvarious red-green-blue (RGB) displays with 1920×1080p and 2560×1600resolutions. It is to be appreciated that embodiments of the inventionare not limited to RGB color schemes or the 1920×1080p or 2560×1600resolutions, and that the specific resolution and RGB color scheme isfor illustrational purposes only.

TABLE 1 Pixel Sub-Pixel Pixels Display Pitch pitch per inch PossibleTransfer Substrate (x, y) (x,y) (PPI) head array pitch 55” (634 μm, (211μm, 40 X: Multiples or fractions of 211 μm 1920 × 1080 634 μm) 634 μm)Y: Multiples or fractions of 634 μm 10” (85 μm, (28 μm, 299 X: Multiplesor fractions of 28 μm 2560 × 1600 85 μm) 85 μm) Y: Multiples orfractions of 85 μm 4” (78 μm, (26 μm, 326 X: Multiples or fractions of26 μm  640 × 1136 78 μm) 78 μm) Y: Multiples or fractions of 78 μm 5”(58 μm. (19 μm. 440 X: Multiples or fractions of 19 μm 1920 × 1080 58μm) 58 μm) Y: Multiples or fractions of 58 μm

In the above exemplary embodiments, the 40 PPI pixel density maycorrespond to a 55 inch 1920×1080p resolution television, and the 326and 440 PPI pixel density may correspond to a handheld device withretina display. In accordance with embodiments of the invention,thousands, millions, or even hundreds of millions of transfer heads canbe included in a micro pick up array of a mass transfer tool dependingupon the size of the micro pick up array. In accordance with embodimentsof the invention, a 1 cm×1.12 cm array of transfer heads can include 837transfer heads with a 211 μm, 634 μm pitch, and 102,000 transfer headswith a 19 μm, 58 μm pitch.

The number of light emitting devices picked up with the array oftransfer heads may or may not match the pitch of transfer heads. Forexample, an array of transfer heads separated by a pitch of 19 μm picksup an array of light emitting micro devices with a pitch of 19 μm. Inanother example, an array of transfer heads separated by a pitch of 19μm picks up an array of light emitting micro devices with a pitch ofapproximately 6.33 μm. In this manner the transfer heads pick up everythird light emitting micro device for transfer to the receivingsubstrate including the reflective bank structure. In accordance withsome embodiments, the top surface of the array of light emitting microdevices is higher than the top surface of the insulating layer so as toprevent the transfer heads from being damaged by or damaging theinsulating layer (or any intervening layer) on the receiving substrateduring placement of the light emitting micro devices within bankopenings in the insulating layer.

FIG. 1 is a side view illustration of an insulating layer formed on asubstrate in accordance with an embodiment of the invention. Substrate100 may be a variety of substrates such as, but not limited to, adisplay substrate, a lighting substrate, a substrate with functionaldevices such as transistors or integrated circuits (ICs), or a substratewith metal redistribution lines. Depending upon the particularapplication, substrate 100 may be opaque, transparent, orsemi-transparent to the visible wavelength (e.g. 380-750 nm wavelength),and substrate 100 may be rigid or flexible. For example, substrate 100may be formed of glass, metal foil, metal foil covered with dielectric,or a polymer such as polyethylene terephthalate (PET), polyethelynenaphthalate (PEN), polycarbonate (PC), polyethersulphone (PES), aromaticfluorine-containing polyarylates (PAR), polycyclic olefin (PCO), andpolyimide (PI).

Insulating layer 110 may be formed by a variety of techniques such aslamination, spin coating, CVD, and PVD. Insulating layer 110 may beopaque, transparent, or semi-transparent to the visible wavelength.Insulating layer 110 may be formed of a variety of materials such as,but not limited to, photodefinable acrylic, photoresist, silicon oxide(SiO₂), silicon nitride (SiN_(x)), poly(methyl methacrylate) (PMMA),benzocyclobutene (BCB), polyimide, acrylate, epoxy, and polyester. In anembodiment, insulating layer is formed of an opaque material such as ablack matrix material. Exemplary insulating black matrix materialsinclude organic resins, glass pastes, and resins or pastes including ablack pigment, metallic particles such as nickel, aluminum, molybdenum,and alloys thereof, metal oxide particles (e.g. chromium oxide), ormetal nitride particles (e.g. chromium nitride).

FIGS. 2A-2J are cross-sectional side view illustrations of a number ofpossible substrates and patterned insulating layer configurations inaccordance with embodiments of the invention. It is to be appreciatedthat the particular embodiments illustrated in FIGS. 2A-2J are intendedto be exemplary and not limiting. Furthermore, the embodimentsillustrated are not necessarily exclusive of one another, and someembodiments illustrated may be combined.

Referring now to FIG. 2A, in an embodiment, an array of bank openings112 are formed in the insulating layer 110 using a suitable techniquesuch as lithography. As illustrated, bank openings 112 may includesidewalls 114A, 114B which are illustrated as being laterally oppositein the figures, and a bottom surface 116. In the embodiment illustratedin FIG. 2A, the bottom surfaces 116 of the bank openings 112 exposes anelectrical line out 102 in the substrate 100. In the embodimentillustrated in FIG. 2B, vias 104 extend between the electrical line out102 and the bottom surfaces 116. Depending upon the particularapplication, electrical line out 102 and vias 104 may be opaque,transparent, or semi-transparent to the visible wavelength. In anembodiment, electrical line out 102 functions as a contact or contactline such as an anode line or cathode line in the completed system. Thematerial of the electrical line out may also be selected for lowresistance, for example, copper.

Exemplary transparent conductive materials include amorphous silicon,poly-silicon, transparent conductive oxides (TCO) such asindium-tin-oxide (ITO) and indium-zinc-oxide (IZO), carbon nanotubefilm, or a transparent conducting polymer such aspoly(3,4-ethylenedioxythiophene) (PEDOT), polyaniline, polyacetylene,polypyrrole, and polythiophene. In an embodiment electrical line out 102is approximately 50 nm-1 μm thick ITO. In an embodiment, the electricalline out 102 and vias 104 include nanoparticles such as silver, gold,aluminum, molybdenum, titanium, tungsten, ITO, and IZO. The electricalline out 102 and vias 104 may also be reflective to the visiblewavelength. In an embodiment, electrical line out 102 and vias 104comprise a reflective metallic film such as aluminum, molybdenum,titanium, titanium-tungsten, silver, or gold, or alloys thereof.

In accordance with embodiments of the invention, the thickness of theinsulating layer 110 and width of the openings 112 described with regardto the following figures may depend upon the height of the lightemitting device to be mounted within the opening, height of the transferheads transferring the light emitting devices, and resolution. In thespecific example of a display substrate, the resolution, pixel density,and subpixel density may account for the width of the openings 112. Foran exemplary 55 inch television with a 40 PPI and 211 μm subpixel pitch,the width may be anywhere from a few microns to 200 μm to account for asurrounding bank structure. For an exemplary display with 326 PPI and a26 μm subpixel pitch, the width may be anywhere from a few microns to 15μm to account for a 5 μm wide surrounding bank structure. For anexemplary display with 440 PPI and a 26 μm subpixel pitch, the width maybe anywhere from a few microns to 17 μm to account for an exemplary 5 μmwide surrounding bank structure. Width of the bank structure may be anysuitable size, so long as the structure supports the required processesand is scalable to the required PPI.

In accordance with embodiments of the invention, the thickness of theinsulating layer 110 is not too thick in order for the reflective bankstructure to function. Thickness may be determined by the light emittingdevice height and a predetermined viewing angle. For example, wheresidewalls of the insulating layer make an angle with the substrate 100,shallower angles may correlate to a wider viewing angle of the system.In an embodiment, exemplary thicknesses of the insulating layer 110 maybe between 1 μm-50 μm.

Referring now to FIG. 2C, in an embodiment, a corresponding array of viaopenings 118 are formed within the insulating layer 110 to expose thesubstrate 100. For example, each via opening 118 may correspond to abank opening 112. In the embodiment illustrated in FIG. 2C, each viaopening 118 exposes a second electrical line out 106 in the substrate100. Second electrical line out 106 may be formed similarly aselectrical line out 102. In an embodiment, electrical line out 106functions as an contact or contact line such as an anode line or cathodeline in the completed system. In an embodiment illustrated in FIG. 2D, asingle via opening 118 is formed within the insulating layer 110 tocorrespond to a plurality of bank openings 112. Via openings 118 mayhave a width which is wide enough to deposit a conductive materialwithin to make electrical contact with the underlying electrical lineout.

Referring now to FIGS. 2E-2J, in some embodiments, the substrate mayinclude circuitry 120 to control the light emitting devices to bemounted. In the embodiments illustrated in FIGS. 2E-2G, a via opening113 is formed in the bottom surface 116 of each bank opening 112 toconnect with an integrated circuit (IC) 120 in substrate 100. In theparticular embodiments illustrated, a corresponding array of ICs 120 areinterconnected with the bottom surfaces 116 of the array of bankopenings 112. In the embodiment illustrated in FIG. 2F, a correspondingarray of via openings 118 are formed within the insulating layer 110 toexpose the substrate 100. For example, each via opening 118 maycorrespond to a bank opening 112. In the embodiment illustrated in FIG.2F, each via opening 118 exposes a second electrical line out 106 in thesubstrate 100. In an embodiment, electrical line out 106 functions as acontact or contact line such as an anode line or cathode line in thecompleted system. In an embodiment electrical line out 106 is connectedwith one or more integrated circuits 120. In an embodiment illustratedin FIG. 2G, a single via opening 118 is formed within the insulatinglayer 110 to correspond to a plurality of bank openings 112. Asillustrated in FIGS. 2E-2F, the electrical lines out 106 may also beinterconnected with the corresponding array of ICs 120.

Referring now to FIGS. 2H-2J, in some embodiments, the bottom surfaces116 of the array of bank openings 112 are on an array of conductivecontact pads 122 interconnected with a corresponding array of ICs 120.Conductive contact pads 122 may be formed of the same materials as theelectrical lines out 102, 106 described above. In the embodimentillustrated in FIG. 2I, a corresponding array of via openings 118 areformed within the insulating layer 110 to expose the substrate 100. Forexample, each via opening 118 may correspond to a bank opening 112. Inthe embodiment illustrated in FIG. 2I, each via opening 118 exposes asecond electrical line out 106 in the substrate 100. Electrical line out106 may function as an contact or contact line such as an anode line orcathode line in the completed system. In an embodiment illustrated inFIG. 2J, a single via opening 118 is formed within the insulating layer110 to correspond to a plurality of bank openings 112. As illustrated inFIGS. 2I-2J, the electrical lines out 106 may also be interconnectedwith the corresponding array of ICs 120.

The receiving substrate 100 in FIGS. 2E-2J may be an active matrix LED(AMLED) backplane. For example, each IC 120 may be a traditional 2T1C(two transistors, one capacitor) circuit including a switchingtransistor, a driving transistor, and a storage capacitor. It is to beappreciated that the 2T1C circuitry is meant to be exemplary, and thatother types of circuitry or modifications of the traditional 2T1Ccircuitry are contemplated in accordance with embodiments of theinvention. For example, more complicated circuits can be used tocompensate for current distribution to the driver transistor and thelight emitting device, or for their instabilities.

FIGS. 3A-3W are cross-sectional side view illustrations of a number ofpossible reflective layer configurations on the substrate and patternedinsulating layer configurations previously described with regard toFIGS. 2A-2J in accordance with embodiments of the invention. It is to beappreciated that the particular embodiments illustrated in FIGS. 3A-3Ware intended to be exemplary and not limiting. Furthermore, theembodiments illustrated are not necessarily exclusive of one another,and some embodiments illustrated may be combined.

Referring to FIG. 3A, in an embodiment, a continuous reflective layer130 is formed over the patterned insulating layer 110 and on thesubstrate 100 within the array of bank openings 112 in the insulatinglayer, and spanning the sidewalls 114A, 114B and the bottom surface 116of each of the bank openings 112 in the insulating layer. The reflectivelayer 130 may be electrically conducting. In an embodiment, thereflective layer 130 functions as an anode or cathode line out.

The reflective layer 130 may be formed of a number of conductive andreflective materials, and may include more than one layer. In anembodiment, a reflective conductive layer 130 comprises a metallic filmsuch as aluminum, molybdenum, titanium, titanium-tungsten, silver, orgold, or alloys thereof. The reflective layer 130 may also include aconductive material which is not necessarily reflective, such asamorphous silicon, transparent conductive oxides (TCO) such asindium-tin-oxide (ITO) and indium-zinc-oxide (IZO), carbon nanotubefilm, or a transparent conducting polymer such aspoly(3,4-ethylenedioxythiophene) (PEDOT), polyaniline, polyacetylene,polypyrrole, and polythiophene. In an embodiment, the reflective layerincludes a stack of a conductive material and a reflective conductivematerial. In an embodiment, the reflective layer includes a 3-layerstack including top and bottom layers and a reflective middle layerwherein one or both of the top and bottom layers are transparent. In anembodiment, the reflective layer includes a conductive oxide-reflectivemetal-conductive oxide 3-layer stack. The conductive oxide layers may betransparent. For example, the reflective layer 130 may include anITO-silver-ITO layer stack. In such a configuration, the top and bottomITO layers may prevent diffusion and/or oxidation of the reflectivemetal (silver) layer. In an embodiment, the reflective layer includes aTi—Al—Ti stack. In an embodiment, the reflective layer includes anITO-Ti-ITO stack. In an embodiment, the reflective layer includes aITO-Ti—Al—Ti-ITO stack. In an embodiment, the reflective layer is 1 μmor less in thickness. The reflective layer may be deposited using asuitable technique such as, but not limited to, PVD.

Still referring to FIG. 3A, a patterned transparent insulator layer 142is optionally formed over the reflective layer 130. The patternedtransparent insulator layer may at least partially cover the insulatinglayer 110 and the reflective layer 130 on the sidewalls 114A, 114B ofthe bank openings 112. The patterned transparent insulator layer 142 mayinclude an array of openings 144 directly over the bottom surface 116 ofthe array of bank openings 112. In an embodiment, the patternedtransparent insulator layer 142 is formed by blanket deposition using asuitable technique such as lamination, spin coating, CVD, and PVD, andthen patterned using a suitable technique such as lithography.Transparent insulator 142 may be formed of a variety of materials suchas, but not limited to, SiO₂, SiN_(x), PMMA, BCB, polyimide, acrylate,epoxy, and polyester. For example, the patterned insulating layer 142may be 0.5 μm thick. The patterned transparent insulator layer 142 maybe transparent or semi-transparent where formed over the reflectivelayer 130 on sidewalls 114A, 114B so as to not significantly degradelight emission extraction of the completed system. Thickness of thepatterned transparent insulator layer 142 may also be controlled toincrease light extraction efficiency, and also to not interfere with thearray of transfer heads during transfer of the array of light emittingdevices to the reflective bank structure. In the following discussion ofFIGS. 3A-3W, each of the illustrated embodiments includes an optionalpatterned transparent insulator layer 142, which may be useful whenforming a top conductive contact described with regard to the systemsillustrated in FIGS. 7A-15D so as to prevent shorting between conductivelayers. As will become more apparent in the following description, thepatterned transparent insulator layer 142 is optional, and representsone manner for electrically separating conductive layers.

Referring now to FIG. 3B, in an embodiment the reflective layer 130 ispatterned into an array of reflective bank layers 132 corresponding tothe array of bank openings 112, for example, using lithography or aphotoresist lift-off technique. A patterned transparent insulator layer142 may then be formed over the array of reflective bank layers 132 andpatterned insulating layer 110. In the embodiment illustrated in FIG.3C, a bonding layer 140 may be deposited on the reflective layer 130covering the bottom surface 116 of the bank opening 112 to aid insecuring the micro light emitting devices, such as a vertical micro LED.For example, bonding layer 140 may include a material such as indium,gold, silver, molybdenum, tin, aluminum, silicon, or an alloy thereof,or transparent conducting polymer, and is approximately 0.1 μm to 1 μmthick. In an embodiment, the thickness of the bonding layer iscontrolled to render the bonding layer transparent to the visiblewavelength. While FIG. 3C is the only illustration in FIGS. 3A-3W of abonding layer 140 formed on the reflective layer 130, it is to beappreciated that in other embodiments a bonding layer 140 may be formedon any of the other reflective layers 130, whether patterned or not, toaid in securing a light emitting device within a bank opening 112. Inthe embodiments illustrated in FIGS. 3A-3C, the reflective layer 130 orarray of reflective bank layers 132 are each illustrated as completelycovering the sidewalls 114A, 114B and bottom surface 116 of each of thebank openings 112. For example, the reflective bank layer 132configuration illustrated in FIGS. 3B-3C may be cone-shaped, with a flatbottom surface.

Referring now to FIGS. 3D-3E, in some embodiments the reflective banklayers 132 span the sidewalls 114A, 114B, and do not completely coverthe bottom surface 116 of the bank openings 112. In an embodiment, thereflective bank layers 132 completely cover the sidewalls 114A, 114B,and do not completely cover the bottom surface 116 of the bank openings112. In the embodiment illustrated in FIG. 3D, the reflective banklayers 132 include a sidewall layer 133 that spans the sidewalls 114A,114B of the corresponding bank opening 112, and a separate pad layer 134on the bottom surface 116 of the corresponding bank opening 112. In thismanner the pad layer 134 is electrically isolated from the sidewalllayer 133. In the embodiment illustrated in FIG. 3E, the reflective banklayers 132 span the sidewalls 114A, 114B of the corresponding bankopenings 112 and do not cover a center of the bottom surface 116 of thecorresponding bank openings 112. In the embodiment illustrated in FIG.3E, a bonding layer 140 may be deposited on the bottom surface 116 ofthe bank opening 112 to aid in securing the micro LED as will bedescribed in further detail below. For example, bonding layer 140 mayinclude a material such as indium, gold, silver, molybdenum, tin,aluminum, silicon, or an alloy, or a transparent conducting polymerthereof and is approximately 50 nm to 1 μm thick. In an embodiment, thethickness of the bonding layer is controlled to render the bonding layertransparent to the visible wavelength. In the embodiment illustrated inFIG. 3E, the bonding layer is electrically isolated from the reflectivebank layer 132 spanning the sidewalls 114A, 114B of the bank openings112.

Referring now to FIGS. 3F-3O, 3Q-3R, 3U-3V, in some embodiments thereflective layer can be patterned and formed over a patterned insulatinglayer including an array of bank openings 112 and one or more viaopenings 118. Following the formation of the reflective layer, atransparent insulator layer 142 may optionally be formed over thepatterned reflective layer and patterned insulating layer. As describedabove, the patterned transparent insulator layer 142 may be formed by,for example, blanket deposition and patterning using a suitabletechnique such as lithography. In the particular embodimentsillustrated, the patterned transparent insulator 142 is illustrated asbeing formed over and between layers 132, 138. However, the patternedtransparent insulator 142 may assume other patterns. For example, insome embodiments the patterned transparent insulator is not formedbetween a reflective via layer 138 and a corresponding reflective banklayer 132. In the embodiments illustrated in FIGS. 3F, 3H, 3J, 3L, 3N,3Q, 3U the reflective layer is patterned to form an array of reflectivebank layers 132 within the array of bank openings 112 and acorresponding separate array of reflective via layers 138 within thearray of via openings 118. In the embodiments illustrated the array ofreflective via layers 138 span sidewalls 115 and a bottom surface 117 ofvia openings 118. In accordance with embodiments of the invention,reflective via layer 138, may function as an electrical line out or beconnected with an electrical line out. In other embodiments, thereflective layer is formed over a patterned insulating layer includingarray of bank openings to form electrical line out 139 and reflectivebank layer 132, as illustrated in FIGS. 3S, 3W.

In the embodiments illustrated in FIGS. 3G, 3I, 3K, 3M, 3O, 3R, 3V thereflective layer is patterned to form an array of reflective bank layers132 within the array of bank openings 112 and a reflective via layer 138within a via opening 118. In the embodiments illustrated, the singlereflective via layer 138 spans sidewalls 115 and a bottom surface 117 ofvia opening 118, and the single reflective layer 138 corresponds to aplurality of reflective bank layers 132. In accordance with embodimentsof the invention, reflective via layer 138, may function as anelectrical line out or be connected with an electrical line out. Inother embodiments, the reflective layer is formed over a patternedinsulating layer including array of bank openings to form electricalline out 139 and reflective bank layer 132.

The embodiments illustrated in FIGS. 3F-3O, 3Q-3R, 3U-3V all include areflective via layer 138 spanning the sidewalls 115 and bottom surface117 of via openings 118. Embodiments of the invention do not require areflective via layer 138 to be formed with the via openings 118. Inother embodiments, the via openings 118 can be filled with anotherconductive material, including the conductive material used to make topcontact with the array of light emitting devices, as described infurther detail below. In other embodiments, such as those illustrated inFIGS. 3S, 3W an electrical line out 139 may be formed from the samematerial as the reflective bank layer 132. In some embodiments, thereflective via layer 138 functions as the electrical line out.

Referring again to the embodiments illustrated in FIGS. 3F-3G, the arrayof reflective bank layers 132 completely cover the sidewalls 114A, 114Band bottom surface 116 of each of the bank openings 112. In theembodiments illustrated in FIGS. 3H-3I, the array of reflective banklayers 132 span a first sidewall 114A, but do not span a laterallyopposite sidewall 114B. In the embodiments illustrated in FIGS. 3J-3Kand 3N-3O, the reflective via layers 138 span sidewalls 115 and a bottomsurface 117 of via openings 118, and across a top surface of thepatterned insulating layer 110, and along a sidewall 114B of an adjacentbank opening 112.

In the embodiments illustrated in FIGS. 3L-3M, the array of reflectivebank layers 132 cover the sidewalls 114A, 114B but do not cover a centerof the bottom surface 116 of each of the bank openings 112. In theparticular embodiments illustrated in FIGS. 3L-3O, an array of bondinglayers 140 are deposited on the bottom surface 116 of the bank openings112 to aid in securing an array of light emitting devices.

Referring now to FIGS. 3P-3W, an array of reflective bank layers 132 maybe formed over the substrates of FIGS. 2E-2J. In the embodimentsillustrated in FIG. 3P-3S, the reflective bank layer 132 is also formedwithin the via openings 113 in the bottom surface 116 of each bankopening 112 to connect with an integrated circuit (IC) 120 in substrate100. In the embodiments illustrated in FIG. 3T-3W, the reflective banklayer 132 is formed on a conductive contact pad 122 interconnected withan IC 120.

FIGS. 4A-4F are cross-sectional side view illustrations of a method ofpicking up and transferring an array of light emitting devices from acarrier substrate to a receiving substrate in accordance with anembodiment of the invention. FIG. 4A is a cross-sectional side viewillustration of an array of light emitting device transfer heads 204supported by substrate 200 and positioned over an array of lightemitting devices 400 stabilized on carrier substrate 300 in accordancewith an embodiment of the invention. The array of light emitting devices400 are then contacted with the array of transfer heads 204 asillustrated in FIG. 4B. As illustrated, the pitch of the array of lightemitting devices 400 may be an integer multiple of the pitch of thearray of transfer heads 204. In the embodiment illustrated the integermultiple is 3 though may be other integer multiples. In an embodiment,the integer multiple may also be 1 so that the pitch of the array oflight emitting devices 400 matches the pitch of the array of transferheads 204. In another embodiment not illustrated, the pitch of the arrayof transfer heads 204 is an integer multiple of the pitch of the arrayof light emitting devices 400. A voltage is applied to the array oftransfer heads 204 to create a grip pressure on the array of lightemitting devices. The voltage may be applied from the working circuitrywithin a transfer head assembly 206 in electrical connection with thearray of transfer heads through vias 207. The array of light emittingdevices 400 is then picked up with the array of transfer heads 204 asillustrated in FIG. 4C, and positioned over a receiving substrate 100including a reflective bank structure as illustrated in FIG. 4D.

The array of light emitting devices 400 is then brought into contactwith the receiving substrate 100 as illustrated in FIG. 4E. In theparticular embodiment illustrated in FIG. 4E, the array of lightemitting devices 400 are brought into contact with the reflective banklayer 132 on the bottom surface 116 of the bank openings 112. The arrayof light emitting devices 400 is then released within the array of bankopenings 112 on receiving substrate 100 as illustrated in FIG. 4F.

In one embodiment, an operation is performed to create a phase change ina bonding layer connecting the array of light emitting devices 400 tothe carrier substrate 300 prior to or while picking up the array oflight emitting devices. For example, the bonding layer may have aliquidus temperature less than 350° C., or more specifically less than200° C. In an embodiment, the bonding layer is a material such as indiumor an indium alloy. If a portion of the bonding layer is picked up withthe light emitting device, additional operations can be performed tocontrol the phase of the portion of the bonding layer during subsequentprocessing. For example, heat can be applied to the bonding layer from aheat source located within the transfer head assembly 206, carriersubstrate 300, and/or receiving substrate 100.

The operation of applying the voltage to create a grip pressure on thearray of light emitting devices can be performed in various orders. Forexample, the voltage can be applied prior to contacting the array oflight emitting devices with the array of transfer heads, whilecontacting the light emitting devices with the array of transfer heads,or after contacting the light emitting devices with the array oftransfer heads. The voltage may also be applied prior to, while, orafter creating a phase change in the bonding layer.

Where the transfer heads 204 include bipolar electrodes, an alternatingvoltage may be applied across a the pair of electrodes in each transferhead 204 so that at a particular point in time when a negative voltageis applied to one electrode, a positive voltage is applied to the otherelectrode in the pair, and vice versa to create the pickup pressure.Releasing the array of light emitting devices from the transfer heads204 may be accomplished with a variety of methods including turning offthe voltage sources, lower the voltage across the pair of siliconelectrodes, changing a waveform of the AC voltage, and grounding thevoltage sources. In an embodiment releasing the array of light emittingdevices is accomplished by altering a waveform of the operating voltagecreating the grip pressure and discharging charge stored in the array oflight emitting devices through the bonding layer 140 or reflective layer130 in the bank structure.

Referring back to FIG. 4E, in some embodiments, the height of thevertical micro LEDs 400 mounted within the array of bank openings 118 isgreater than the thickness of the insulating layer 110. Having the topsurface of the array of vertical micro LEDs higher than the top surfaceof the insulating layer 110 and any intervening layers may prevent anyidle transfer heads from being damaged by or damaging the insulatinglayer (or any intervening layer) on the receiving substrate duringplacement of the vertical micro LEDs within the bank openings. Forexample, where insulating layer 110 is 2 μm thick, each vertical microLED 400 is 2 μm thick or thicker. For example, where insulating layer is30 μm thick, each vertical micro LED 400 is 30 μm thick or thicker. Inan embodiment, the height of each transfer head 204 may be between 2-20μm. Accordingly, some amount of clearance may be provided by virtue ofthe height of the transfer heads 204, and it may not be required in allembodiments for the top surface of the array of vertical micro LEDs toraise above the top surface of the insulating layer 110 and anyintervening layers.

In the following description with regard to FIGS. 5A-15G variouscross-sectional side view and top view illustrations are provided forintegrating an array of light emitting devices with a number of possibleconfigurations of the substrate and patterned insulating layerconfigurations of FIGS. 2A-2J with the reflective layer configurationsof FIGS. 3A-3W in accordance with embodiments of the invention. It is tobe appreciated that the particular embodiments illustrated in FIGS.5A-15G are intended to be exemplary and not limiting. Furthermore, theembodiments illustrated are not necessarily exclusive of one another,and some embodiments illustrated may be combined.

Referring now to FIG. 5A, in an embodiment, an array of light emittingdevices are mounted within the reflective bank structure for a topemitting system, as indicated by the direction of the dotted arrowlines. The specific embodiment illustrated in FIG. 5A corresponds to thereflective bank structure previously described with regard to FIG. 3Bwithout the optional transparent insulator layer, though it isunderstood that a number of other reflective bank structures will alsobe useful in a top emitting system. FIG. 5B is a top view illustrationof FIG. 5A, with the side view illustration of FIG. 5A taken along lineA-A in FIG. 5B. As illustrated, the array of reflective bank structures132 may be formed in a cone-like shape with a flat bottom surface andsidewalls laterally surrounding the light emitting devices 400. Thoughembodiments of the invention are not limited to such, and may assume avariety of configurations such as polygon, square, rectangle, oval, etc.Referring again to FIG. 5A, a close up illustration is provided of avertical micro LED device 400 in accordance with an embodiment. It is tobe appreciated, that the specific vertical micro LED device 400illustrated is exemplary and that embodiments of the invention are notlimited. For example, embodiments of the invention may also beapplicable to other devices such as, but not limited to, the micro LEDdevices in U.S. patent application Ser. No. 13/372,222, U.S. patentapplication Ser. No. 13/436,260, U.S. patent application Ser. No.13/458,932, and U.S. patent application Ser. No. 13/625,825 all of whichare incorporated herein by reference. Embodiments of the invention mayalso be applicable to other devices which are designed in such a way soas to perform a photonic function (LED, SLD, laser).

In the particular embodiment illustrated, the vertical micro LED device400 includes a micro p-n diode 450 and a bottom electrode 420. A bondinglayer (not illustrated) may optionally be formed below the bottomelectrode 420, with the bottom electrode 420 between the micro p-n diode450 and the bonding layer. In an embodiment, the vertical micro LEDdevice 400 further includes a top electrode 470. In an embodiment, thevertical micro LED device 400 is several microns thick, such as 30 μm orless, or even 5 μm or less, and the top and bottom electrodes 470, 420are each 0.1 μm-2 μm thick. In an embodiment, a maximum width of eachvertical micro LED device 400 is 1-100 μm, for example 30 μm, 10 μm, or5 μm.

The top electrode 470 and/or bottom electrode 420 may include one ormore layers and can be formed of a variety of electrically conductingmaterials including metals, conductive oxides, and conductive polymers.The top and bottom electrodes 470, 420 may be transparent orsemi-transparent to the visible wavelength range (e.g. 380 nm-750 nm) oropaque. The top and bottom electrodes 470, 420 may optionally include areflective layer, such as a silver layer.

In an embodiment, the micro p-n diode 450 includes a top n-doped layer414, one or more quantum well layers 416, and a lower p-doped layer 418.In an alternative embodiment, the top doped layer 414 is p-doped, andthe lower doped layer 418 is n-doped. The micro p-n diodes can befabricated with straight sidewalls or tapered sidewalls. In certainembodiments, the micro p-n diodes 450 possess outwardly taperedsidewalls 453 (from top to bottom). In certain embodiments, the microp-n diodes 450 possess inwardly tapered sidewall (from top to bottom).

The micro p-n diode and bottom electrode may each have a top surface, abottom surface and sidewalls. In an embodiment, the bottom surface 451of the micro p-n diode 450 is wider than the top surface 452 of themicro p-n diode, and the sidewalls 453 are tapered outwardly from top tobottom. The top surface of the micro p-n diode 450 may be wider than thebottom surface of the p-n diode, or approximately the same width. In anembodiment, the bottom surface 451 of the micro p-n diode 450 is widerthan the top surface of the bottom electrode 420. The bottom surface ofthe micro p-n diode may also be approximately the same width as the topsurface of the bottom electrode 420. In an embodiment the top surface ofthe micro p-n diode is approximately the same width as the top electrode470.

Still referring to FIG. 5A, in an embodiment the sidewalls 453 form anangle θ₁ with the bottom surface 451 of the micro p-n diode 450, and thesidewalls 114 form an angle θ₂ with top surface of the substrate 100. Asillustrated angles θ₁ and θ₂ are both formed along a plane parallel tothe top surface of the substrate. In an embodiment, θ₂ is smaller thanθ₁ and is in the opposite direction. For example, in an embodiment,angle θ₁ is between +90 and +85 degrees, and θ₂ is between −85 and −30degrees, or more specifically between −40 and −60 degrees with respectto the top surface of the substrate 100. It is to be appreciated thatthe angular relationships illustrated are exemplary, and in otherembodiments, for example, θ₁ may have a negative value rather thanpositive value (i.e. inwardly tapered sidewalls).

Referring now to FIG. 6A, in an embodiment, an array of light devicesare mounted within the reflective bank structure for a top and bottomemitting system, as indicated by the direction of the dotted arrowlines. The specific embodiment illustrated in FIG. 6A corresponds to thereflective bank structure previously described with regard to FIG. 3Ewithout the optional transparent insulator layer, though it isunderstood that a number of other reflective bank structures will alsobe useful in a top and bottom emitting system. FIG. 6B is a top viewillustration of FIG. 5A, with the side view illustration of FIG. 6Ataken along line A-A in FIG. 6B. In the embodiment illustrated thereflective bank layers 132 on sidewalls 114A, 114B form rings around thelight emitting devices 400. Though embodiments of the invention are notlimited to such, and may assume a variety of configurations such aspolygon, square, rectangle, oval, etc. A number of modifications can beperformed to increase top or bottom emission, such as including areflective layer in either of the top electrode 470 or bottom electrode420, or including a reflective layer (such as a reflective conductivecontact layer) over or under the light emitting device 400.

Referring now to FIGS. 7A-7B, in some embodiments, an array of lightemitting devices are mounted within the reflective bank structuredescribed with regard to FIG. 3A. In the particular embodimentsillustrated, the optional transparent insulator layer 142 is notpresent, though it may be present in other embodiments. As illustrated,after the transfer of the array of light emitting devices 400, asidewall passivation layer 150 may be formed around the sidewalls of thelight emitting devices 400 within the array of bank openings 112. In anembodiment, where the light emitting devices are vertical LED devices,the sidewall passivation layer 150 covers and spans the quantum wellstructure 416. The sidewall passivation layer 150 may also be formedover the continuous reflective layer 130 on top of the patternedinsulating layer 110 in order to electrically insulate the reflectivelayer 130 from the top conductive contact layer 160. In the embodimentillustrated in FIG. 7A, a patterned top conductive contact layer 160 isformed over each light emitting device 400 in electrical contact withthe top electrode 470, if present. In the embodiment illustrated in FIG.7B, a continuous top conductive contact layer 160 is formed over eachlight emitting device 400 and in electrical contact with the topelectrodes 470, if present.

In accordance with embodiments of the invention, the sidewallpassivation layer 150 may be transparent or semi-transparent to thevisible wavelength so as to not significantly degrade light extractionefficiency of the completed system. Sidewall passivation layer may beformed of a variety of materials such as, but not limited to epoxy,poly(methyl methacrylate) (PMMA), benzocyclobutene (BCB), polyimide, andpolyester. In an embodiment, sidewall passivation layer 150 is formed byink jetting around the light emitting devices 400.

Depending upon the particular application in the following description,top conductive contact layer 160 may be opaque, reflective, transparent,or semi-transparent to the visible wavelength. For example, in topemission systems the top conductive contact may be transparent, and forbottom emission systems the top conductive contact may be reflective.Exemplary transparent conductive materials include amorphous silicon,transparent conductive oxides (TCO) such as indium-tin-oxide (ITO) andindium-zinc-oxide (IZO), carbon nanotube film, or a transparentconductive polymer such as poly(3,4-ethylenedioxythiophene) (PEDOT),polyaniline, polyacetylene, polypyrrole, and polythiophene. In anembodiment top conductive contact layer 160 is approximately 50 nm-1 μmthick ITO-silver-ITO stack. In an embodiment, the top conductive contactlayer 160 includes nanoparticles such as silver, gold, aluminum,molybdenum, titanium, tungsten, ITO, and IZO. In a particularembodiment, the top conductive contact 160 is formed by ink jetting.Other methods of formation may include chemical vapor deposition (CVD),physical vapor deposition (PVD), spin coating. The top conductivecontact layer 160 may also be reflective to the visible wavelength. Inan embodiment, a top conductive contact layer 160 comprises a reflectivemetallic film such as aluminum, molybdenum, titanium, titanium-tungsten,silver, or gold, or alloys thereof.

FIG. 7C is a top view illustration of FIG. 7A prior to formation of thesidewall passivation layer 150 and top conductive contact layer 160 inaccordance with an embodiment of the invention. FIGS. 7D-7E arecross-sectional side view illustrations of the array of light emittingdevices of FIG. 7A in electrical contact with an electrical line out ofFIG. 2A in accordance with embodiments of the invention. As shown a toppassivation layer 170 is formed over the array of light emitting devicesof FIG. 7A. In embodiments where top conductive layer 160 istransparent, the top passivation layer 170 may also be transparent orsemi-transparent so as to not degrade light extraction efficiency of thesystem. Top passivation layer 170 may be formed of a variety ofmaterials such as, but not limited to, silicon oxide (SiO₂), siliconnitride (SiN_(g)), poly(methyl methacrylate) (PMMA), benzocyclobutene(BCB), polyimide, and polyester, and may be formed by a variety ofmethods including chemical vapor deposition (CVD), physical vapordeposition (PVD), spin coating. The embodiments illustrated in FIGS.7D-7E differ in that the embodiment of FIG. 7E includes a transparentinsulator layer 142, while the embodiment of FIG. 7D does not. As shown,the inclusion of the transparent insulator layer 142 may assist inelectrically isolating the reflective layer 130 from the top conductivecontact 160.

FIGS. 7F-7G are cross-sectional side view illustrations of the array oflight emitting devices of FIG. 7B in electrical contact with anelectrical line out of FIG. 2A in accordance with embodiments of theinvention. FIGS. 7F-7G differ in that the embodiment of FIG. 7G includesa transparent insulator layer 142, while the embodiment of FIG. 7F doesnot. As shown, the inclusion of the transparent insulator layer 142 mayassist in electrically isolating the reflective layer 130 from the topconductive contact 160.

Referring now to FIGS. 8A-8B, in some embodiments an array of lightemitting devices are mounted within the reflective bank structuredescribed with regard to FIG. 3B with or without the optionaltransparent insulator layer 142. As illustrated, after the transfer ofthe array of light emitting devices 400, a sidewall passivation layer150 may be formed around the sidewalls of the light emitting devices 400within the array of bank openings 112 similarly as described with regardto FIGS. 7A-7B. In the embodiment illustrated in FIG. 8A, a patternedtop conductive contact layer 160 is formed over each light emittingdevice 400 in electrical contact with the top electrode 470, if present.In the embodiment illustrated in FIG. 8B, a continuous top conductivecontact layer 160 is formed over each light emitting device 400 and inelectrical contact with the top electrodes 470, if present.

FIG. 8C is a top view illustration of FIG. 8A prior to formation of thesidewall passivation layer 150 and top conductive contact layer 160 inaccordance with an embodiment of the invention. FIGS. 8D-8E arecross-sectional side view illustrations of the array of light emittingdevices of FIG. 8A in electrical contact with an electrical line out ofFIG. 2A in accordance with embodiments of the invention. In anotherembodiment, the electrical line out of FIG. 2B may be incorporated. Asshown a top passivation layer 170 is formed over the array of lightemitting devices of FIG. 8A. The embodiments illustrated in FIGS. 8D-8Ediffer in that the embodiment of FIG. 8E includes a transparentinsulator layer 142, while the embodiment of FIG. 8D does not. As shown,the inclusion of the transparent insulator layer 142 may assist inelectrically isolating the reflective bank layers 132 from the topconductive contact 160.

FIGS. 8F-8G are cross-sectional side view illustrations of the array oflight emitting devices of FIG. 8B in electrical contact with anelectrical line out of FIG. 2A in accordance with embodiments of theinvention. In another embodiment, the electrical line out of FIG. 2B maybe incorporated. FIGS. 8F-8G differ in that the embodiment of FIG. 8Gincludes a transparent insulator layer 142, while the embodiment of FIG.8F does not. As shown, the inclusion of the transparent insulator layer142 may assist in electrically isolating the reflective bank layers 132from the top conductive contact 160.

Referring now to FIGS. 9A-9B, in some embodiments an array of lightemitting devices are mounted within the reflective bank structuredescribed with regard to FIG. 3D. As illustrated, after the transfer ofthe array of light emitting devices 400, a sidewall passivation layer150 may be formed around the sidewalls of the light emitting devices 400within the array of bank openings 112 similarly as described with regardto FIGS. 7A-7B. As shown the pad layer 134 is electrically isolated fromthe sidewall layer 133. In the embodiment illustrated in FIG. 9A, apatterned top conductive contact layer 160 is formed over each lightemitting device 400 in electrical contact with the top electrode 470, ifpresent, and reflective sidewall layer 133. In the embodimentillustrated in FIG. 9B, a continuous top conductive contact layer 160 isformed over each light emitting device 400 and in electrical contactwith the top electrodes 470, if present, and reflective sidewall layer133.

FIG. 9C is a top view illustration of FIG. 9A prior to formation of thesidewall passivation layer 150 and top conductive contact layer 160 inaccordance with an embodiment of the invention. FIGS. 9D-9E arecross-sectional side view illustrations of the array of light emittingdevices of FIG. 9A in electrical contact with an electrical line out ofFIG. 2B in accordance with embodiments of the invention. As shown a toppassivation layer 170 is formed over the array of light emitting devicesof FIG. 9A. The embodiments illustrated in FIGS. 9D-9E differ in thatthe embodiment of FIG. 9E includes a transparent insulator layer 142,while the embodiment of FIG. 9D does not. As shown, the inclusion of thetransparent insulator layer 142 may assist in electrically isolating thereflective bank layers 132 from the top conductive contact 160.

In the following embodiments described with regard to any of FIGS.10A-15G, one or more reflective via layers 138 may be described andillustrated. In accordance with embodiments of the invention, thereflective via layers 138 may function as an electrical line out orconnect with an electrical line out. Reflective via layers 138 may alsobe replaced with other electrically conducting materials. In otherembodiments, vias are not formed in the insulating layer 110, and thereflective via layers 138 are replaced by electrical lines out 139, asillustrated in FIGS. 14F-14G, 15F-15G. Accordingly, in any of thefollowing embodiments the reflective via layers 138 may function as anelectrical line out, connect with an electrical line out, be replacedwith other electrically conducting materials, or be replaced byelectrical lines out 139.

Referring now to FIGS. 10A-10B, in some embodiments an array of lightemitting devices are mounted within the reflective bank structuredescribed with regard to FIG. 3F. As illustrated, after the transfer ofthe array of light emitting devices 400, a sidewall passivation layer150 may be formed around the sidewalls of the light emitting devices 400within the array of bank openings 112 similarly as described with regardto FIGS. 7A-7B. In the embodiment illustrated in FIGS. 10A-10B, apatterned top conductive contact layer 160 is formed over each lightemitting device 400 in electrical contact with the top electrode 470, ifpresent, and within via openings 118 and in contact with reflective vialayers 138, if present. FIG. 10C is a top view illustration of FIGS.10A-10B prior to formation of the sidewall passivation layer 150 and topconductive contact layer 160 in accordance with an embodiment of theinvention. FIG. 10D is a top view illustration of FIGS. 10A-10B afterformation of the sidewall passivation layer 150 and top conductivecontact layer 160 in accordance with an embodiment of the invention. Asshown, FIG. 10A is a side view illustration taken along lines A-A inFIG. 10C-10D, and FIG. 10B is a side view illustration taken along linesB-B in FIG. 10C-10D.

Referring again to FIG. 10D, top conductive contact layer 160 mayinclude portions 160A formed over the light emitting device 400 andreflective bank layer 132, portions 160C formed over the via openings118 and in contact with the reflective via layer 138, if present, and atrace portion 160B extending between portions 160A and 160C. Referringnow to FIGS. 10E-10F, in an embodiment, the top electrodes of the arrayof light emitting devices 400 are in electrical contact with electricallines out 106 of FIG. 2C with the top conductive contact layer 160. Theembodiments illustrated in FIGS. 10D-10F differ in that the embodimentof FIG. 10F includes a transparent insulator layer 142, while theembodiment of FIG. 10E does not. In the embodiments illustrated, eachtop conductive contact layer 160 is electrically separated from anadjacent top conductive contact layer, so that an array of topconductive contact layers 160 correspond to an array of light emittingdevices 400. In this manner, the resistance of the top conductivecontact layer 160 can be reduced by minimizing length and area, and theelectrical lines out 102, 106 can be formed of a material with lowerresistivity than the top conductive contact layer 160. For example, topconductive layer 160 may be formed of ink jet PEDOT, with the electricallines out 102, 106 being formed of lower resistivity copper. In thismanner, the top conductive contact layer 160 may span a comparativelyshorter distance than electrical line out 106, resulting in a totalsignal line with lower resistance. In the particular embodimentsillustrated, the patterned transparent insulator 142 is illustrated asbeing formed over and between layers 132, 138. However, the patternedtransparent insulator layer 142 may assume other patterns. For example,in some embodiments the patterned transparent insulator layer 142 is notformed between a reflective via layer 138 and a corresponding reflectivebank layer 132 since the top conductive contact layer 160 makeselectrical contact to reflective via layer 138. Such a configuration maybe employed in any of the following embodiments (e.g. 10H, 10J, 11F,11H, 11I, 11J, 12F, 12H, 12J, 13G, 13I, 13K, 13M, 14C-14G, 15C-15G)illustrating an optional patterned transparent insulator layer 142.

Many of the embodiments that follow are illustrated and described with atop conductive contact layer 160 being in contact with a reflective vialayer 138. It is to be appreciated however, that the reflective vialayer 138 is optional. The reflective via layer 138 may be replaced witha non-reflective conductive material. Alternatively, the top conductivecontact layer 160 may be formed within the via openings 118 and makecontact with an electrical line out 106.

Referring now to FIGS. 10G-10H, in an embodiment, a continuous topconductive contact layer 160 is formed over each light emitting device400 and in electrical contact with the top electrodes 470, if present,and an electrical line out 106 of FIG. 2C. As illustrated, thecontinuous top conductive contact layer 160 is in electricalcommunication with an array of light emitting devices 400 and a singleelectrical line out 106. The embodiments illustrated in FIGS. 10G-10Hdiffer in that the embodiment of FIG. 10H includes a transparentinsulator layer 142, while the embodiment of FIG. 10G does not. Asshown, the inclusion of the transparent insulator layer 142 may assistin electrically isolating the reflective bank layers 132 from the topconductive contact 160.

Referring now to FIGS. 10I-10J, in an embodiment, a continuous topconductive contact layer 160 is formed over each light emitting device400 and in electrical contact with the top electrodes 470, if present,and an electrical line out 106 of FIG. 2D. As illustrated, thecontinuous top conductive contact layer 160 is in electricalcommunication with an array of light emitting devices 400 and a singleelectrical line out 106. The embodiments illustrated in FIGS. 10I-10Jdiffer in that the embodiment of FIG. 10J includes a transparentinsulator layer 142, while the embodiment of FIG. 10I does not. Asshown, the inclusion of the transparent insulator layer 142 may assistin electrically isolating the reflective bank layers 132 from the topconductive contact 160.

Referring now to FIGS. 11A-11B, in some embodiments, an array of lightemitting devices are mounted within the reflective bank structuredescribed with regard to FIG. 3H. The embodiments illustrated in FIGS.11A-11B are similar to those of FIGS. 10A-10B, with the exception of thereflective bank layer 132 does not completely cover the sidewalls of thebank opening 112. As shown in FIG. 11A, the reflective bank layer 132 isformed on sidewall 144A, and is not formed along sidewall 114B nearest acorresponding via opening 118. FIG. 11C is a top view illustration ofFIG. 11A prior to formation of the sidewall passivation layer and topconductive contact in accordance with an embodiment of the invention.FIG. 11D is a top view illustration of FIG. 11A after formation of thesidewall passivation layer and top conductive contact in accordance withan embodiment of the invention. As shown, FIG. 11A is a side viewillustration taken along lines A-A in FIG. 11C-11D, and FIG. 11B is aside view illustration taken along lines B-B in FIG. 11C-11D.

Referring now to FIGS. 11C-11D, in an embodiment, the reflective banklayer 132 does not completely cover the sidewalls of the bank opening.Top conductive contact layer 160 may include portions 160A formed overthe light emitting device 400 and reflective bank layer 132, portions160C formed over the via openings 118 and in contact with the reflectivevia layer 138, if present, and a trace portion 160B extending betweenportions 160A and 160C. In the embodiment illustrated, the reflectivebank layer 132 is not formed on the sidewall of the bank opening 112nearest the via opening 118. In such an embodiment, this may relievepatterning tolerances to avoid potential shorting between the reflectivebank layer 132 and top conductive contact layer 160 spanning between thevia opening 118 and bank opening 112.

FIGS. 11E-11F are cross-sectional side view illustrations of the arrayof light emitting devices of FIG. 11A in electrical contact with anelectrical line out of FIG. 2C in accordance with embodiments of theinvention. The embodiments illustrated in FIGS. 11E-11F differ in thatthe embodiment of FIG. 11F includes a transparent insulator layer 142,while the embodiment of FIG. 11E does not. In the embodimentsillustrated, each top conductive contact layer 160 is electricallyseparated from an adjacent top conductive contact layer, so that anarray of top conductive contact layers 160 correspond to an array oflight emitting devices 400. In this manner, the resistance of the topconductive contact layer 160 can be reduced by minimizing length andarea, and the electrical lines out 102, 106 can be formed of a materialwith lower resistivity than the top conductive contact layer 160.

Referring now to FIGS. 11G-11H, in an embodiment, a continuous topconductive contact layer 160 is formed over each light emitting device400 and in electrical contact with the top electrodes 470, if present,and an electrical line out 106 of FIG. 2C. As illustrated, thecontinuous top conductive contact layer 160 is in electricalcommunication with an array of light emitting devices 400 and a singleelectrical line out 106. The embodiments illustrated in FIGS. 11G-11Hdiffer in that the embodiment of FIG. 11H includes a transparentinsulator layer 142, while the embodiment of FIG. 11G does not. Asshown, the inclusion of the transparent insulator layer 142 may assistin electrically isolating the reflective bank layers 132 from the topconductive contact 160.

Referring now to FIGS. 11I-11J, in an embodiment, a continuous topconductive contact layer 160 is formed over each light emitting device400 and in electrical contact with the top electrodes 470, if present,and an electrical line out 106 of FIG. 2D. As illustrated, thecontinuous top conductive contact layer 160 is in electricalcommunication with an array of light emitting devices 400 and a singleelectrical line out 106. The embodiments illustrated in FIGS. 11I-11Jdiffer in that the embodiment of FIG. 11J includes a transparentinsulator layer 142, while the embodiment of FIG. 11I does not. Asshown, the inclusion of the transparent insulator layer 142 may assistin electrically isolating the reflective bank layers 132 from the topconductive contact 160.

Referring now to FIGS. 12A-12B, in some embodiments, an array of lightemitting devices are mounted within the reflective bank structuredescribed with regard to FIG. 3J. The embodiments illustrated in FIGS.12A-12B are similar to those of FIGS. 10A-10B, with the exception of thereflective bank layer 132 does not completely cover the sidewalls of thebank opening 112, and the reflective via layer 138 covers a sidewall ofthe bank opening 112. As shown in FIG. 11A, the reflective bank layer132 is formed on sidewall 144A, and reflective via layer 138 coverssidewall 114B nearest a corresponding via opening 118. FIG. 12C is a topview illustration of FIG. 12A prior to formation of the sidewallpassivation layer and top conductive contact in accordance with anembodiment of the invention. FIG. 12D is a top view illustration of FIG.12A after formation of the sidewall passivation layer and top conductivecontact in accordance with an embodiment of the invention. As shown,FIG. 12A is a side view illustration taken along lines A-A in FIG.12C-12D, and FIG. 12B is a side view illustration taken along lines B-Bin FIG. 12C-12D.

Referring now to FIGS. 12C-12D, in an embodiment, the reflective banklayer 132 does not completely cover the sidewalls of the bank opening,and the reflective via layer 138 covers a sidewall of the bank opening112. In the embodiment illustrated, the reflective bank layer 132 andreflective via layer 138 are electrically isolated from one another. Topconductive contact layer 160 may include portions 160A formed over thelight emitting device 400, portions 160C formed over the via openings118 and in contact with the reflective via layer 138 and a trace portion160B extending between portions 160A and 160C. In the embodimentillustrated, the reflective via layer 138 is formed on the sidewall ofthe bank opening 112 nearest the via opening 118. In an embodiment, suchconfiguration may allow for reduced length of the top conductive layer.While the top conductive layers 160 are illustrated as completelyextending over the via openings 118, this may not be required. Inanother embodiment, the top conductive layer 160 may only contact thereflective via layer 138 on top of the patterned insulating layer 110.

FIGS. 12E-12F are cross-sectional side view illustrations of the arrayof light emitting devices of FIG. 12A in electrical contact with anelectrical line out of FIG. 2C in accordance with embodiments of theinvention. The embodiments illustrated in FIGS. 12E-12F differ in thatthe embodiment of FIG. 12F includes a transparent insulator layer 142,while the embodiment of FIG. 12E does not. In the embodimentsillustrated, each top conductive contact layer 160 is electricallyseparated from an adjacent top conductive contact layer, so that anarray of top conductive contact layers 160 correspond to an array oflight emitting devices 400. In this manner, the resistance of the topconductive contact layer 160 can be reduced by minimizing length andarea, and the electrical lines out 102, 106 can be formed of a materialwith lower resistivity than the top conductive contact layer 160.

Referring now to FIGS. 12G-12H, in an embodiment, a continuous topconductive contact layer 160 is formed over each light emitting device400 and in electrical contact with the top electrodes 470, if present,and an electrical line out 106 of FIG. 2C. As illustrated, thecontinuous top conductive contact layer 160 is in electricalcommunication with an array of light emitting devices 400 and a singleelectrical line out 106. The embodiments illustrated in FIGS. 12G-12Hdiffer in that the embodiment of FIG. 12H includes a transparentinsulator layer 142, while the embodiment of FIG. 12G does not. Asshown, the inclusion of the transparent insulator layer 142 may assistin electrically isolating the reflective bank layers 132 and reflectivevia layers 138 from the top conductive contact 160.

Referring now to FIGS. 12I-12J, in an embodiment, a continuous topconductive contact layer 160 is formed over each light emitting device400 and in electrical contact with the top electrodes 470, if present,and an electrical line out 106 of FIG. 2D. As illustrated, thecontinuous top conductive contact layer 160 is in electricalcommunication with an array of light emitting devices 400 and a singleelectrical line out 106. The embodiments illustrated in FIGS. 12I-12Jdiffer in that the embodiment of FIG. 12J includes a transparentinsulator layer 142, while the embodiment of FIG. 12I does not. Asshown, the inclusion of the transparent insulator layer 142 may assistin electrically isolating the reflective bank layers 132 and reflectivevia layer 138 from the top conductive contact 160.

Referring now to FIGS. 13A-13B, in some embodiments an array of lightemitting devices are mounted within the reflective bank structuredescribed with regard to FIG. 3E. As illustrated, after the transfer ofthe array of light emitting devices 400, a sidewall passivation layer150 may be formed around the sidewalls of the light emitting devices 400within the array of bank openings 112 similarly as described with regardto FIGS. 9A-9B. As shown the bonding layer 140 is electrically isolatedfrom the reflective bank layer 132. In the embodiment illustrated inFIG. 13A, a patterned top conductive contact layer 160 is formed overeach light emitting device 400 in electrical contact with the topelectrode 470, if present, and reflective bank layer 132. Contacting thereflective bank layer 132 may keep the reflective bank layer 132 fromfloating within the structure. In another embodiment, the top conductivecontact layer 160 does not contact the reflective bank layer 132, andthe reflective bank layer 132 is floating. In the embodiment illustratedin FIG. 13B, a continuous top conductive contact layer 160 is formedover each light emitting device 400 and in electrical contact with thetop electrodes 470, if present, and reflective bank layer 132.Alternatively, the reflective bank layers 132 may be allowed to float.

FIG. 13C is a top view illustration of FIG. 13A prior to formation ofthe sidewall passivation layer 150 and top conductive contact layer 160in accordance with an embodiment of the invention. FIG. 13D is across-sectional side view illustration of the array of light emittingdevices of FIG. 13A in electrical contact with an electrical line out ofFIG. 2B in accordance with embodiments of the invention. As shown a toppassivation layer 170 is formed over the array of light emitting devicesof FIG. 13A. FIG. 13E is a cross-sectional side view illustration of thearray of light emitting devices of FIG. 13B in electrical contact withan electrical line out of FIG. 2B in accordance with embodiments of theinvention. As shown a top passivation layer 170 is formed over the arrayof light emitting devices of FIG. 13B.

FIGS. 13F-13G are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3L in electrical contact with anelectrical line out of FIG. 2C in accordance with embodiments of theinvention. The embodiments illustrated in FIGS. 13F-13G differ in thatthe embodiment of FIG. 13G includes a transparent insulator layer 142,while the embodiment of FIG. 13F does not. As shown, the inclusion ofthe transparent insulator layer 142 may assist in electrically isolatingthe reflective bank layers 132 from the top conductive contact 160.

FIGS. 13H-13I are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3M in electrical contact with anelectrical line out of FIG. 2D in accordance with embodiments of theinvention. The embodiments illustrated in FIGS. 13H-13I differ in thatthe embodiment of FIG. 13I includes a transparent insulator layer 142,while the embodiment of FIG. 13H does not. As shown, the inclusion ofthe transparent insulator layer 142 may assist in electrically isolatingthe reflective bank layers 132 from the top conductive contact 160.

FIG. 13J-13K are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3N in electrical contact with anelectrical line out of FIG. 2C in accordance with embodiments of theinvention. The embodiments illustrated in FIGS. 13J-13K differ in thatthe embodiment of FIG. 13K includes a transparent insulator layer 142,while the embodiment of FIG. 13J does not. As shown, the inclusion ofthe transparent insulator layer 142 may assist in electrically isolatingthe reflective bank layers 132 from the top conductive contact 160.

FIG. 13L-13M are cross-sectional side view illustration of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3O in electrical contact with anelectrical line out of FIG. 2D in accordance with embodiments of theinvention. The embodiments illustrated in FIGS. 13L-13M differ in thatthe embodiment of FIG. 13M includes a transparent insulator layer 142,while the embodiment of FIG. 13L does not. As shown, the inclusion ofthe transparent insulator layer 142 may assist in electrically isolatingthe reflective bank layers 132 from the top conductive contact 160.While not illustrated, in other embodiments, the top contact layer 160illustrated in FIGS. 13E-13M may be replaced by an array of patternedtop contact layers 160 as previously described and illustrated.

FIG. 14A-14B are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3P in accordance with embodiments of theinvention. As illustrated, after the transfer of the array of lightemitting devices 400, a sidewall passivation layer 150 may be formedaround the sidewalls of the light emitting devices 400 within the arrayof bank openings 112 similarly as described with regard to FIGS. 8A-8B.In the embodiments illustrated in FIGS. 14A-14B, a continuous topconductive contact layer 160 is formed over each light emitting device400 and in electrical contact with the top electrodes 470, if present.The embodiments illustrated in FIGS. 14A-14B differ in that theembodiment of FIG. 14B includes a transparent insulator layer 142, whilethe embodiment of FIG. 14A does not. As shown, the inclusion of thetransparent insulator layer 142 may assist in electrically isolating thereflective bank layers 132 from the top conductive contact 160.

FIG. 14C is cross-sectional side view illustration of an array of lightemitting devices mounted within the reflective bank structure describedwith regard to FIG. 3Q in accordance with an embodiment of theinvention. In the embodiment illustrated in FIG. 14C, a continuous topconductive contact layer 160 is formed over an array of light emittingdevices 400 and in electrical contact with the top electrodes 470, ifpresent, and in contact with an array reflective via layers 138, ifpresent.

FIG. 14D is cross-sectional side view illustration of an array of lightemitting devices mounted within the reflective bank structure describedwith regard to FIG. 3R in accordance with an embodiment of theinvention. In the embodiment illustrated in FIG. 14D, a continuous topconductive contact layer 160 is formed over an array of light emittingdevice 400 and in electrical contact with the top electrodes 470, ifpresent, and in contact with a single reflective via layers 138, ifpresent.

FIGS. 14E-14G are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuresdescribed with regard to FIG. 3S in accordance with embodiments of theinvention. In the embodiment illustrated in FIG. 14E, a continuous topconductive contact layer 160 is formed over an array of light emittingdevices 400 and in electrical contact with the top electrodes 470, ifpresent, and in contact with an array of electrical lines out 139. Inthe embodiment illustrated in FIG. 14F, a continuous top conductivecontact layer 160 is formed over an array of light emitting device 400and in electrical contact with the top electrodes 470, if present, andin contact with a single electrical line out 139.

While FIGS. 14A-14F have been illustrated as including a continuous topconductive contact layer, in alternative embodiments, a patterned topconductive contact layer 160 may be formed over each light emittingdevice 400 in electrical contact with the top electrode 470, if present,as previously described and illustrated. For example, in an embodimentto FIG. 14G the top contact layer 160 may be replaced by an array ofpatterned top contact layers 160 formed over an array of light emittingdevices 400 and in electrical contact with the top electrodes 470, ifpresent, and in contact with an array of electrical lines out 139.Further, while FIGS. 14C-14G have been illustrated as including atransparent insulator layer 142, in other embodiments, a transparentinsulator layer 142 is not present.

FIG. 15A-15B are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuredescribed with regard to FIG. 3T in accordance with embodiments of theinvention. As illustrated, after the transfer of the array of lightemitting devices 400, a sidewall passivation layer 150 may be formedaround the sidewalls of the light emitting devices 400 within the arrayof bank openings 112 similarly as described with regard to FIGS. 8A-8B.In the embodiments illustrated in FIGS. 15A-15B, a continuous topconductive contact layer 160 is formed over each light emitting device400 and in electrical contact with the top electrodes 470, if present.The embodiments illustrated in FIGS. 15A-15B differ in that theembodiment of FIG. 15B includes a transparent insulator layer 142, whilethe embodiment of FIG. 15A does not. As shown, the inclusion of thetransparent insulator layer 142 may assist in electrically isolating thereflective bank layers 132 from the top conductive contact 160.

FIG. 15C is cross-sectional side view illustration of an array of lightemitting devices mounted within the reflective bank structure describedwith regard to FIG. 3U in accordance with an embodiment of theinvention. In the embodiment illustrated in FIG. 15C, a continuous topconductive contact layer 160 is formed over an array of light emittingdevice 400 and in electrical contact with the top electrodes 470, ifpresent, and in contact with an array reflective via layers 138, ifpresent.

FIG. 15D is cross-sectional side view illustration of an array of lightemitting devices mounted within the reflective bank structure describedwith regard to FIG. 3V in accordance with an embodiment of theinvention. In the embodiment illustrated in FIG. 15D, a continuous topconductive contact layer 160 is formed over an array of light emittingdevice 400 and in electrical contact with the top electrodes 470, ifpresent, and in contact with a single reflective via layer 138, ifpresent.

FIGS. 15E-15G are cross-sectional side view illustrations of an array oflight emitting devices mounted within the reflective bank structuresdescribed with regard to FIG. 3W in accordance with embodiments of theinvention. In the embodiment illustrated in FIG. 15E, a continuous topconductive contact layer 160 is formed over an array of light emittingdevices 400 and in electrical contact with the top electrodes 470, ifpresent, and in contact with an array of electrical lines out 139. Inthe embodiment illustrated in FIG. 15F, a continuous top conductivecontact layer 160 is formed over an array of light emitting device 400and in electrical contact with the top electrodes 470, if present, andin contact with a single electrical line out 139.

While FIGS. 15A-15F have been illustrated as including a continuous topconductive contact layer, in alternative embodiments, a patterned topconductive contact layer 160 may be formed over each light emittingdevice 400 in electrical contact with the top electrode 470, if present,as previously described and illustrated. For example, in an embodimentto FIG. 15G the top contact layer 160 may be replaced by an array ofpatterned top contact layers 160 formed over an array of light emittingdevices 400 and in electrical contact with the top electrodes 470, ifpresent, and in contact with an array of electrical lines out 139.Further, while FIGS. 15C-15G have been illustrated as including atransparent insulator layer 142, in other embodiments, a transparentinsulator layer 142 is not present.

In utilizing the various aspects of this invention, it would becomeapparent to one skilled in the art that combinations or variations ofthe above embodiments are possible for mounting an array of lightemitting devices within a reflective bank structure. Although thepresent invention has been described in language specific to structuralfeatures and/or methodological acts, it is to be understood that theinvention defined in the appended claims is not necessarily limited tothe specific features or acts described. The specific features and actsdisclosed are instead to be understood as particularly gracefulimplementations of the claimed invention useful for illustrating thepresent invention.

What is claimed is:
 1. A light emitting structure comprising: asubstrate; a group of conductive contact pads on the substrate, whereineach conductive contact pad is coupled to a corresponding drivingtransistor in the substrate; an insulating layer over the substrate; agroup of bank openings in the insulating layer, each bank openingexposing a corresponding conductive contact pad; a group of verticallight emitting diode devices the group of conductive contact pads withinthe group of bank openings.
 2. The light emitting structure of claim 1,wherein each vertical light emitting diode device in the group ofvertical light emitting diode devices includes a micro p-n diode thatincludes a top p-doped or n-doped layer, a lower p-doped or n-dopedlayer, and one or more quantum well layers between the top and lowerp-doped or n-doped layers, and wherein the micro p-n diode includes oneor more layers based on II-VI materials or III-V materials.
 3. The lightemitting structure of claim 2, wherein each vertical light emittingdiode device in the group of vertical light emitting diode devices has amaximum width of 1 μm-100 μm.
 4. The light emitting structure of claim3, wherein each vertical light emitting diode device in the group ofvertical light emitting diode devices has a maximum width of 1 μm-5 μm.5. The light emitting structure of claim 3, wherein each vertical lightemitting diode device in the group of vertical light emitting diodedevices has a maximum thickness of 5 μm or less.
 6. The light emittingstructure of claim 3, wherein no vertical light emitting diode device ofthe group of vertical light emitting diode devices spans along asidewall of a corresponding bank opening.
 7. The light emittingstructure of claim 3, further comprising a sidewall passivation layerformed around sidewalls of the group of vertical light emitting diodesdevices.
 8. The light emitting structure of claim 7, further comprisinga top conductive contact layer spanning over the sidewall passivationlayer and the group of vertical light emitting diode devices, and inelectrical contact with the group of vertical light emitting diodedevices.
 9. The light emitting structure of claim 8, further comprisinga via opening though the insulating layer, wherein the top conductivecontact layer is electrically connected with an electrical line outthrough the via opening.
 10. The light emitting structure of claim 8,further comprising an electrical line out over the insulating layer,wherein the top conductive contact layer is electrically connected withthe electrical line out.
 11. The light emitting structure of claim 8,wherein each conductive contact pad of the group of conductive contactpads is reflective to the visible wavelength range of 380 nm-750 nm. 12.The light emitting structure of claim 11, wherein each conductivecontact pad includes a multiple-layer stack.
 13. The light emittingstructure of claim 12, wherein the multi-layer stack includes a metalliclayer selected from the group consisting of silver, aluminum, andtitanium.
 14. The light emitting structure of claim 8, furthercomprising a group of laterally separate reflective bank layers withinthe group of bank openings in the insulating layer.
 15. The lightemitting structure of claim 14, wherein each laterally separatereflective bank layer includes a multiple-layer stack.
 16. The lightemitting structure of claim 15, wherein the multi-layer stack includes ametallic layer selected from the group consisting of silver, aluminum,and titanium.